Box2DFlashAS3 2.1a的类库

Box2D的很好的flash开源类库,Box2D的flash as3 2.1版本，里面有API,实例源文件；Box2D类库；(Box2D's very good flash open source class library, Box2D flash AS3 2.1 version, which has API, instance source files; Box2D class library;)